P0402 (bad catalytic converter) AGAIN after replacing catalytic converter?

[viaVolvo]

A short bit of background. This question is for a 2005 S40 2.4i (manual transmission) that I just picked up for less than 1/2 of book and I'm thrilled with it. It is gorgeous, in wonderful shape, and I have repair receipts for the last 3 years or so which is very helpful. (More about that in a bit.) The previous owner lived in a rural area and had his mechanical work done by a small town shop (not at a Volvo dealership).

I'm actually getting two codes right now and they may be related (?)

Code 1 is P2407
Exercising my Google Fu I come up with this:


Code 2 is P0402 (most commonly, a bad catalytic converter) as seen here:



I just took delivery of this car on Sunday. Receipts tell me that on 10-10-16 the owner had the Catalytic Converter replaced along with Oxygen Sensor 1 and Sensor 2. (With an oil change, the bill was $1091.) The owner told me that since listing it on Craigslist, the Check Engine light had come on again and so he slashed the price for me to take it as is. Between my negotiations and picking up the car, the owner took it in to get the codes read and told me that it was an EVAP code and indicated a cracked fuel cap. He offered me the good price along with a New Fuel Cap and a full tank of gas. He said that the light was now off, which it was when I looked at and drove the car. I bought it and drove it 233 miles to my folks' place. The CEL was still off and the gas tank was half full. I wanted to know what my gas mileage on the trip was so I filled it up. (Got 32.5 mpg mostly 65 mph). The next day I started for home from my folks'. I did a bit of city driving on the way, but about 170 miles into the trip (100 of which was interstate/79 mph) the fuel gauge was slightly below 1/2 and the CEL came on. I can not tell any difference in the way the car runs/sounds.

So, looking at those two images (above) of the possible culprits:
Is there something that could cause both codes?
What order would you try checking/fixing? (For example, I think that checking/blowing out/cleaning the Purge Valve is a no-cost thing to try.)
I put in gas with 10% ethanol (87 or 89 octane, which is common around here.) Is it important to use higher octane premium to help avoid this issue?
Any other words of wisdom or insight would be greatly appreciated.

PS... this S40 is going to be my daily driver (it has 126K and is replacing a Jetta with 179K). Our "good" car is a 2013 XC70 that has been superb so far (40K).

Thanks in advance and I will report back with what I do (what works and what doesn't).

Darren

[matthew1]

Darren, welcome. I shared this on the MVS Facebook page to get more ideas. (I don't know the answer.)

[MadeInJapan]

I'm wondering if they went with generic Oxy sensors (or even Bosch but still the wrong ones)...they are culprits on other Volvos- I would think they would reak havoc on our cars as well.

[oragex]

as above... was it original O2 sensor and cat.. ? even then, the CEL light doesn't mean you need replacing the cat again. Several things can trigger a CEL light, of which some are important - such as a misfire, while others don't require an urgent repair, such as an exhaust or vacuum leak

[jimmy57]

Octane of fuel has zero bearing on this.
DOes the engine run smooth and idle smooth?
A common cause of that code is a partially clogged injector tip. That, and a few other 2001 and later volvo non turbo engines, use a multiple hole spray tip with extra fine holes. The holes can plug easily and when this happens the fuel mixture is off on that cylinder (lean) and the ECM will correct until oxygen level is read as correct. the problem is that the lean cylinder(s) will have too much O2 and the richening will drive the OK injector cylinders rivh and the O2 level average will be fine as far as O2 sensor can read. BUT the catalyst will not process exhaust correctly with the errant exhaust gas and rear O2 sensor will not read the correct value for properly functioning catalyst.

[MadeInJapan]

After reading the last response, I would be tempted to first put something in the gas that would clean the injectors- maybe Seafoam? Then, if that doesn't work, maybe even re-working the injectors to see if that might makes a difference.